Serve mostly to weakness but vary the placement and spin some. A 20% variation is enough to keep opponent guessing.

发球主要发往对手的弱点，但是偶而也要变换落点和旋转，只要有20%的变化就可以让对手难以捉摸。

youdao

Serve mostly to weakness but vary the placement and spin some. A 20% variation is enough to keep opponent guessing.

发球主要发往对手的弱点，但是偶而也要变换落点和旋转，只要有20%的变化就可以让对手难以捉摸。

youdao